Chronic obstructive pulmonary disease (COPD) is a disease of the respiratory apparatus, characterized by an irreversible obstruction of the airways, of a degree that varies according to the gravity. Chronic obstructive pulmonary disease is usually progressive and is associated to a state of chronic inflammation of the pulmonary tissue. The long-term consequence is an outright remodelling of the bronchi, which causes a considerable reduction in respiratory capacity.
COPD frequently causes a change in body conformation, consisting in a loss of weight and of muscle mass. The prevalence of underweight is 35-60% in COPD of a moderate-to-severe type, whilst the prevalence of reduction of muscle mass is approximately 20% in clinically stable forms. Alterations of body composition have a negative impact on organs and body districts of the patient, ultimately reducing their respiratory and peripheral-musculature function, motor autonomy, capacity of defense against infections, cognitive functions, state of health, and survival, irrespective of the degree of obstruction of the airways. At 10 years from onset of chronic obstructive pulmonary disease the survival rate is 40%.
Numerous factors concur in alterations of body composition, from inadequacy of the caloric intake, especially in periods of acute exacerbation of the disease, to alterations of protein balance on account of the prevalence of protein catabolism over the processes of protein synthesis.
Given the extent of the prognosticated reduction in vital functions and life expectancy, numerous studies have investigated into the best strategy to enable prevention, correction or limitation of weight loss, above all loss in muscle mass, induced by COPD, and investigations are still in progress. Fundamentally, these studies have adopted three approaches: i) nutritional intervention; ii) pharmacological intervention; iii) integrated nutrition-rehabilitation intervention.
All three approaches present, however, serious limits.
The nutritional supplementation based upon an incremented protein-caloric intake improves body weight and respiratory-musculature function. However, clinical practice highlights the fact that patients with severe COPD are highly unlikely to be able to introduce 2300-2500 kcal each day with the food.
Pharmacological interventions have demonstrated very limited results. For example, the use of megestrol, a progestational molecule with the effect of stimulating the appetite, induces an increase in weight due to increase in fat mass but not in lean (muscle) mass. Anabolic steroids (growth hormone, testosterone, stanazolol, oxandrolone) induces minor increases in fat-free mass, but no clear improvement of the functional and pulmonary state.
Nutritional supplementation with approximately 600 kcal, when inserted in a programme of respiratory rehabilitation of the duration of 8 weeks, is able to improve weight, muscle mass, maximum respiratory pressure, muscular strength, capacity for physical exercise in underweight patients with COPD. However, there exists the major limit that many patients do not have the possibility of access to rehabilitation carried out in hospital regime or do not manage to carry out intense physical exercise.